Hibernate Validator’s ResourceBundleMessageInterpolator generates two instances of ResourceBundleLocator one for UserDefined validation Standard validation messages – defaultResourceBundleLocator.
Posted Date:- 2021-08-21 06:52:34
It is the Reference of the handle of the association attribute of the many views as the benefit of the mappedBy attribute, Hibernate has all the erudition it needs. With these processes, we need to define a bidirectional many-to-one association.
Posted Date:- 2021-08-21 06:50:12
Identity :
1. It is database software dependent.
2. Id field mapped column must have auto increment constraint.
3. consider deleted value while generating new id value.
4. Database software use id value after inserting record.
Increment :
1. It is database software independent.
2. Id field mapped column not required.
3. Deleted value does not consider while generating new id value.
4. Hibernate software generate id value.
Posted Date:- 2021-08-21 06:31:27
Assigned Generator is the default generator if no generator is configured.
Posted Date:- 2021-08-21 06:28:38
Hibernate gives set of pre-defined algorithms as identity value generator to generate identity value for hibernate domain class object while saving them to database.
All the generator classes implements the org.hibernate.id.IdentifierGenerator interface. The application programmer may create one’s own generator classes by implementing the IdentifierGenerator interface. Hibernate framework provides many built-in generator classes:
1. assigned
2. increment
3. sequence
4. hilo
5. native
6. identity
7. seqhilo
8. uuid
9. guid
10. select
11. foreign
12. sequence-identity
Posted Date:- 2021-08-21 06:26:02
The process of keeping track of how many times, the loaded object is modified through hibernate persistance logic is known as versioning.
To implement this feature in our project we just need to add “@Version†annotation in our entity class.
Example :
@Version
@Column(name=â€ver_colâ€)
private int version;
Posted Date:- 2021-08-21 06:24:36
@Entity annotation is used to declare a class as an entity.
Example
@Entity
@Table(name="posts")
public class Post{
String title;
String description;
}
Posted Date:- 2021-08-21 06:15:43
Hibernate query language, HQL is an object-oriented extension to SQL. It allows you to query, store, update, and retrieve objects from a database without using SQL.
This question is also similar to the earlier question about Criterion query, Java developers who have not used Hibernate extensively will not know much about features like HQL and Criterion.
Posted Date:- 2021-08-21 06:14:18
TimeToIdleSeconds enables cached object to be invalidated if it has not been requested for specified ('timeToIdleSeconds' ) seconds.
TimeToLiveSeconds enables cached object to be invalidated after that many seconds regardless of how many times or when cache was requested last time.
Posted Date:- 2021-08-21 06:10:42
We can use session contains() method to check if an object is present in the hibernate cache or not, if the object is found in cache, it returns true or else it returns false.
Posted Date:- 2021-08-21 06:09:45
There are 4 different CacheMode.
1. CacheMode.NORMAL : This mode allows to read and write data in second level cache.
2. CacheMode.GET : In this mode, data will be read but will not be written in second level cache.
3. CacheMode.PUT : Data will be written but not will be read from second level cache.
4. CacheMode.REFRESH : Data will be written and will not be read from second level cache. The difference between Put and Refresh is that CacheMode.
Posted Date:- 2021-08-21 06:09:15
1. ENABLE_SELECTIVE: Entities will not be cached until entity will be annotated by cacheable.
2. DISABLE_SELECTIVE : Those entities are cached which are explicitly not annotated with cacheable.
3. ALL : Every entities will be cached.
4.NONE: No entity will be cached.
Posted Date:- 2021-08-21 06:07:30
The below are the advantages of EHCache. (org.hibernate.cache.EhCacheProvider)
It is fast.
lightweight.
Easy-to-use.
Supports read-only and read/write caching.
Supports memory-based and disk-based caching.
Posted Date:- 2021-08-21 06:05:03
Second level cache is on SessionFactory level. All the second level cache provider class must implement org.hibernate.cache.spi.CacheProvider by configuring the property hibernate.cache.provider_class. Hibernate provides open source cache providers also.
Posted Date:- 2021-08-21 06:02:56
Session.save() it’s used for saving the object in the database and session.persist() for transient, persistent objects.
Posted Date:- 2021-08-21 06:00:21
Hibernate supports various object states. One of this object state is transient. In hibernate which is object relation mapping, it will map or create every variable with the class we have defined. For example, if we declare a new variable it will add its entry to the database. But if a variable is marked @Transient then it will not be added to the database. This means it has no persistence representation in that hibernate session. And after an application is closed these transient objects will be destroyed through garbage collection.
class Edufect{
private int id;
private String courseName;
@Transient
private int courseId;
}
So in this in our database, we can see the entry of id column, courseName but no courseId column. But if we remove transient annotation from courseId then it will be added as an int to the database.
Posted Date:- 2021-08-21 05:58:49
Spring and Hibernate are two different things, Spring has several components like Dependency Injection, Spring MVC, Spring ORM, Spring Rest API. So Spring ORM and Hibernate are kind of similar, they both deal with the object relation model, which means they deal with connection java objects to database entities.
Now if you want to build a Rest API using Spring, you can use the Spring Rest API (Here is the getting start guide for Spring Rest Building a RESTful Web Service) for ORM you can either choose Hibernate or Spring ORM framework in either cases there are advantages and disadvantages but major industry goes with using Hibernate (I might be wrong!!) I’ve used both of them Spring ORM is quite useful in simple scenarios and Hibernate in some complex scenarios, whereas in most complex scenarios both of them are not quite useful when you want to write really complex queries. (Both of them provide functionalities two write queries by yourself in the case of complex scenarios).
Posted Date:- 2021-08-21 05:57:37
Hibernate maps Java data types into databases. Java type can be mapped into one or more column in the database. We can set the Object’s record as primitive types like int, byte or more complex, for example, java.util.Currency.
Data types supported in Hibernate are
1. Primitive types.
2. Date and time types.
3. Binary and large object types.
4. Other JDK-related types.
Posted Date:- 2021-08-21 05:56:37
There are multiple ways to use join in Hibernate.
1. Using relationships such as one-to-one, one-to-many or many-to-many
2. Using joins in native SQL query
3. Using joins in HQL
Posted Date:- 2021-08-21 05:52:55
There are three strategies supported by Hibernate. You can use xml files or JPA annotation to implement them.
1. Table per Hierarchy
2. Table per concrete class
3. Table per subclass
Posted Date:- 2021-08-21 05:51:51
1. Sorted Collection
2. Ordered Collection
Posted Date:- 2021-08-21 05:50:23
Important interfaces of Hibernate framework are:
SessionFactory (org.hibernate.SessionFactory)
It is an immutable thread safe cache of compiled mappings for a single database.
We are supposed to initialize SessionFactory once and then we are allowed to cache and reuse it.
The SessionFactory instance is used to return the session objects for database operations.
Session (org.hibernate.Session)
It is a single threaded and short-lived object, which represents a conversation between the persistent store and the application.
The session should be opened only when it is required and should be closed as soon as the user is done.
The session object is the interface between hibernate framework and Java application code and it provides methods for the CRUD operations.
Transaction (org.hibernate.transaction)
It is a single threaded and short-lived object used by the application, which specifies atomic units of work.
The application is abstracted from the underlying JDBC or JTA transaction.
Posted Date:- 2021-08-21 05:49:36
It is a technique in where the objects are loaded on the requirement basis. Since the Hibernate 3 version, the lazy loading is by default enabled so that the child objects are not loaded while the parent is loaded.
Posted Date:- 2021-08-21 05:46:52
save(): stores object in database. It generates identifier for tQhe object and returns it. If object already exists in database, it will throw an error.
saveOrUpdate(): SaveOrUpdate method save the object if identifies does not exist. If it exists , it calls update method.
Posted Date:- 2021-08-21 05:45:41
HQL stands for Hibernate query language. It is very simple, efficient and object oriented query languages which simplifies complex SQL queries. Instead of table, you use object to write queries.
Posted Date:- 2021-08-21 05:44:54
Yes, you can declare entity class as final but it is not considered as a good practice because hibernate uses proxy pattern for lazy initialisation, If you declare it as final then hibernate won’t be able to create sub class and won’t be able to use proxy pattern, so it will limit performance and improvement options.
Posted Date:- 2021-08-21 05:44:02
Criteria objects are used to create and execute object-oriented Queries to retrieve the objects.
Posted Date:- 2021-08-21 05:42:35
The Key components of Hibernate are:
Session: It is used to get a physical network with a database.
Transaction: It represents the unit of work with a database.
Query: It uses SQL and HQL string to retrieve the data from the database and create objects.
Criteria: It is used to create and execute object-oriented queries and retrieve the objects.
Configuration: It represents the properties of files required by Hibernate
Session Factory: It configures hibernate for the application using the provided configuration file and instantiates the session object.
Posted Date:- 2021-08-21 05:41:36
Getting() and load() which are used for fetching data for the assigned identifier. Get() method return null,load() method throws error of object not found type of exception.
Posted Date:- 2021-08-21 05:40:25
Join-Fetching and Select Fetchings are the fetchings available in Hibernate.
Posted Date:- 2021-08-21 05:39:51
We can execute native SQL query in hibernate with the help of SQLQuery object. Still, We should avoid this approach because we cannot use the benefits of hibernate first-level caching and hibernate association.
Posted Date:- 2021-08-21 05:36:00
Hibernate Tools plugin helps the users in writing hibernate configuration and mapping files quickly. The primary benefit is the content assist in assisting the user with different properties and XML tags to use. It validates them against the Hibernate DTD files, so the user knows any mistakes beforehand.
Posted Date:- 2021-08-21 05:35:12
First level caching: It starts with each session basis, with a “session†object.
Second level caching: It can be shareable beyond multiple sessions.
Posted Date:- 2021-08-21 05:34:30
Entity beans are containers, classes, descriptors. Hibernate is a tool that instantly persists the object tree to a class.
Posted Date:- 2021-08-21 05:33:49
ORM Tool, Hibernate provides a powerful query language (HQL)
Posted Date:- 2021-08-21 05:33:25
It’s always useful to allow a servlet container to manage the connection pool as the user so that we define JNDI resource for DataSource, and we can use it in the web application. It’s straightforward to use in Hibernate, all we need is to remove all the database-specific properties and use the below feature to provide the JNDI DataSource name.
Example
<property name="hibernate.connection.datasource">java:comp/env/jdbc/MyLocalDB</property>
Posted Date:- 2021-08-21 05:32:50
We can quickly implement relationships like One to One Mapping, One to Many Mapping, and Many to Many Mappingusing JPA annotations as well as XML based configurations.
Posted Date:- 2021-08-21 05:31:56
We can use the Hibernate Session merge() to update existing values; however, this method creates a copy from the passed entity object and returns it. The returned object is part of the persistent context and tracked for any changes; the given object is not tracked. For example, a program, read Hibernate merge.
Posted Date:- 2021-08-21 05:29:16
1. A one to one association is similar to many to one association, and only one difference is that it must be set as a unique one. We can use many to one element to define one to one association.
2. A name attribute must set in the parent class, and the column attribute is used to set a column name in the parent table for the defined variable. It is unique so that only one object gets associated with another.
Posted Date:- 2021-08-21 05:28:49
Query interface is object oriented representation of Hibernate Query. You can get query object bu calling Session.createQuery() method.
Here is simple example to execute Native query using Query APIs.
SQLQuery query = session.createSQLQuery("select name, age from Employee");
List<Object[]> rows = query.list();
for(Object[] row : rows){
Employee e = new Employee();
e.setName(row[0].toString());
e.setAge(Integer.parseInt(row[1].toString()));
System.out.println(e);
}
Posted Date:- 2021-08-21 05:26:43
This association is the common type of association where one object can be associated with multiple objects.
And Many-to-one element defines the Many-to-One association.To the defined variable, a name attribute is set in the parent class and column attribute sets the column name in the parent table.
Posted Date:- 2021-08-21 05:24:59
In this association, one object can be associated with multiple objects.
The One-to-Many mapping is implemented using a Set Java collection that does not have any redundant element.
A One-to-Many element of the set element indicates the relation of one object to multiple objects.
Posted Date:- 2021-08-21 05:24:28
These objects use SQL and HQL string to retrieve data from the database and create objects.
An instance of Query is used to bind query parameters, restrict the number of results returned by the query and finally to execute the query.
Posted Date:- 2021-08-21 05:22:14
It represents a unit of work with the database and most of the RDBMS (Relational Database Management System) supports transaction functionality.
In Hibernate, transactions are managed by an underlying transaction manager and transaction from JDBC or JTA.
It is an optional object and the Hibernate Application do not use this interface, instead, they handle the transactions in their code.
Posted Date:- 2021-08-21 05:21:18
SessionFactory is heavy weight object and it should be created one per database. SessionFactory object is shared by multiple sessions.
Posted Date:- 2021-08-21 05:19:58
Session interface is primarily used by hibernate application. Session is light weight,short lived objects which are inexpensive to create and destroy. It allows you to create query objects to retrieve persistent objects.It wraps JDBC connection Factory for Transaction.It holds a mandatory (first-level) cache of persistent objects, used when navigating the object graph or looking up objects by identifier .
Posted Date:- 2021-08-21 05:18:42
1. Session
2. SessionFactory
3. Configuration
4. Transaction
5. Query and Criteria interface.
Posted Date:- 2021-08-21 05:18:22
ORM stands for Object Relational mapping. It is programming paradigm which is used to persist java objects to database tables.
Posted Date:- 2021-08-21 05:16:33
Apart from Persistence i.e. saving and loading data from Database, Hibernate also provides the following benefits
1) Caching
2) Lazy Loading
3) Relationship management and provides code for mapping an object to the data
4) The developer is free from writing code to load/store data into the database.
Posted Date:- 2021-08-21 05:15:49
Hibernate is an ORM (Object-relational Mapping) framework, which allows the developer to concentrate on business logic by taking care of the persistence of data by itself.Java developer can write code using an object and Hibernate can take care of creating those object from data loaded from the database and saving update back to the database.
Posted Date:- 2021-08-21 05:14:57